In Austin, TX, I saw $5.50-6.50... most were around $6.50. Kool-Cote tried to give me a starting price of something crazy like $5 per sq ft (on top of the cost of the concrete I paid). They quickly came down to $1.85 (supposedly builder price). Note that kool cote is cheaper on new concrete since they don't have to grind it to make it level.
We interviewed like 5 patio guys. Don't recommend the craigslist approach. Ultimately, we found two great ways of identifying good concrete people: 1) recommended by our other contractors that we used, 2) does the concrete work for x, y, and z major builders. The guy we ultimately went with is well known in Austin, is used by the top builders, and has been in the business 20+ years (he was like 50 so he just oversaw the work).
In terms of amount of concrete, I recommend doing as much as you can. At the urging of TFP, we doubled our initial amount and are glad we did. I wouldn't want any more than we did because I still want to retain room for soccer with the kids, but I'm glad we upped it (800 sq ft vs ~400).